Benzoxazine compounds have been employed satisfactorily to produce prepregs, laminates, moulding material, RTM (resin transfer moulding) systems, sealants, sinter powders, cast articles, structural composites parts, varnishes, surface coatings, electrical and electronic components by impregnating, coating, laminating or moulding processes. Such resins are dimension stable and have good electrical and mechanical resistance, low shrinkage, low water absorption, medium to high glass transition temperatures and good retaining properties, in term of mechanical properties.
Benzoxazine compounds can easily be produced in several, well known ways by the reaction of bisphenols with a primary amine and formaldehyde, whereby the process can be carried out in the presence of solvents (see for example U.S. Pat. No. 5,152,993 or U.S. Pat. No. 5,266,695) or in the absence of solvents (see for example U.S. Pat. No. 5,543,516). The common manufacture and various curing possibilities using hardeners such as novolacs, polyepoxides or polyamines optionally together with a catalyst, or the catalytical and/or thermal curing as well as the valuable properties of the resins make this class of thermosetting resins attractive.
EP 0 789 056 A2 describes a thermosetting resin composition with improved curability comprising dihydrobenzoxazines of polyphenols such as novolacs or bisphenol A and novolac phenolic resins. The composition is used as adhesives or for the manufacture of moulded articles, coatings, sealings, prepregs for printed wiring boards and metal-clad laminates with low water absorbance, improved none-flammability and high heat resistance. The use of polyhydroxy functional novolacs results in sometimes undesirable high reactivities (low gel times) and in higher cross-linked resins, which in general are more brittle.
WO 2006/035021 A1 describes bisbenzoxazines on the basis of phenolphthalein for the preparation of polymers, which show a high temperature stability and a good none-flammability. Polymerisation may be carried out in presence of catalytic amounts of catalysts, such as thiodipropionic acid, phenols or sulfonyl diphenol. The use of bisphenols as hardeners is not mentioned in WO 2006/035021 A1.
WO 00/27921 A1 discloses a ternary composition comprising 10 to 80 weight percent of a benzoxazine monomer, 10 to 80 weight percent of an epoxy reactant and 1 to 80 weight percent of a phenolic resin or phenolic compound. The use of bisphenols as hardeners for thermosetting compositions comprising bis(dihydrobenzoxazine) is not disclosed in WO 00/27921 A1.